Synthesis and crystal structures of 5,17-di-bromo-26,28-dihy-droxy-25,27-dipropynyloxycalix[4]arene, 5,17-di-bromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene and 25,27-bis-(2-azido-eth-oxy)-5,17-di-bromo-26,28-di-hydroxy-calix[4]arene.

The calixarenes, 5,17-di-bromo-26,28-dihy-droxy-25,27-dipropynyloxycalix[4]arene (CHBrO, ), 5,17-di-bromo-26,28-dipropoxy-25,27-dipropynyloxycalix[4]arene (CHBrO, ) and 25,27-bis-(2-azido-eth-oxy)-5,17-di-bromo-26,28-di-hydroxy-calix[4]arene (CHBrNO, ) possess a pinched cone mol-ecular shape for and , and a 1,3-alternate shape for compound . In calixarenes and , the cone conformations are additionally stabilized by intra-molecular O-H⋯O hydrogen bonds, while in calixarene intra-molecular Br⋯Br inter-actions consolidate the 1,3-alternate mol-ecular conformation. The dense crystal packing of the cone dialkyne is a consequence of π-π, C-H⋯π and C-H⋯O inter-actions.

Switchable silver-ion complexation by triazolated calix[4]semitubes.

Triazolated calix[4]semitubes comprising several binding sites were studied for complexation of Ag to get insight into the ability of the multitopic semi-tubular environment to host cation(s) in a structure-specific/switchable manner. For this purpose, a series of triazolated calix[4]semitubes having two or three 1,3-alternate calix[4]arene cores and crown-5-ether loops in the structures were prepared using the recently developed stepwise synthesis approach. Crown-5-ether loops were used as model receptor units which could be filled with K to charge positively either a specific 'end' or both 'ends' of the semi-tubular assemblies and to affect the complexation abilities of the internal binding sites of triazolated calix[4]semitubes.